Stone-in-place casting is now a widely used method in the jewelry industry. Three aspects of the technique that distinguish it from conventional casting are the wax patterns used, the special investment powder needed for diamonds and the firing cycle for the flasks. The production of the wax pattern from a master model is a critical step. The variables involved are described. A comparison of the properties of conventional and stone-casting investments is given. The consequences of adding boric acid to investment are detailed. Investment that is specially formulated for casting with stones needs a lower burnout temperature than conventional investments. The reasons for this and implications for good burnout are described.

Author: Dr. Ian McKeer